KR20160104306A - Method for Drying Optical Film - Google Patents

Abstract

The present invention provides a drying method of an optical film, which returns an optical film through a drying furnace in which a plurality of guide rolls for bending a return route of the optical film are installed, and arranges a heating plate rotator to rotate between the guide rolls while the heating plate rotator contacts the optical film to contact-dry the optical film. According to the drying method of the present invention, the optical film is uniformly dried and drying efficiency is increased to reduce difference in a width direction moisture content and to prevent width direction color unevenness and smudges.

Description

TECHNICAL FIELD The present invention relates to a method for drying an optical film,

The present invention relates to a drying method of an optical film, and more particularly, to a drying method of an optical film capable of preventing occurrence of unevenness in color direction in a width direction and unevenness which is a problem in a non-contact drying method using hot air.

BACKGROUND ART Polarizers used in various image display devices including liquid crystal display devices (LCDs) are usually produced by coating a polyvinyl alcohol (PVA) -based film with at least one polarizing agent on which dichroic dye is adsorbed, And has a structure in which a polarizer protective film typified by cellulose triacetylcellulose (TAC) film is laminated.

As the adhesive used for bonding the polarizer of the polarizing plate to the protective film, a water-based adhesive favorable to stability and environmental friendliness of the solution is often used. After the polarizing plate and the protective film are bonded, a drying process is performed.

The drying process may be performed by spraying hot air. As shown in FIG. 1, the conveying path of the optical film 10 is bent by the plurality of guide rolls 32a and 32b, (See Japanese Laid-Open Patent Application No. 2013-120256).

However, in the above-described method, the hot air discharged in the vertical direction from the hot air outlet 34a of the hot air injection tube 34 provided in the horizontal direction on the upper and lower sides of the drying furnace 30 is not uniformly transmitted to the optical film, Color unevenness and unevenness occur.

Japanese Laid-Open Patent Application No. 2013-120256

An object of the present invention is to provide a drying method of an optical film capable of preventing occurrence of widthwise color heterogeneity and unevenness which is a problem in a non-contact drying method using hot air .

Another object of the present invention is to provide a method for producing a polarizing plate using the drying method.

On the other hand, in the present invention, the optical film is conveyed through the drying furnace provided with the plurality of guide rolls for bending the conveyance path of the optical film, and the heating plate rotating body is rotated between the guide rolls in contact with the optical film And drying the optical film by contacting and drying the optical film.

In one embodiment of the present invention, the heating plate rotating body includes an annular heating plate rotating in contact with the optical film, and a plurality of heating rolls rotating at a fixed position inside the annular heating plate, The annular heating plate can be supported and rotated.

In one embodiment of the present invention, the heating plate rotator may be arranged to move in a state in which the optical film is in contact with the upper surface of one heating plate rotating body, and then move in contact with the lower surface.

In another embodiment of the present invention, the heating plate rotating body is disposed in two stages in the drying furnace so that the optical film moves in contact with the upper surface of the first heating plate rotating body, and then the second heating plate rotating body As shown in Fig.

In one embodiment of the present invention, the optical film may be a polarizing plate.

In one embodiment of the present invention, the temperature of the drying furnace may be 40 to 100 캜.

On the other hand, the present invention provides a method for producing a polarizing plate in which a protective film is bonded to at least one surface of a polarizer using an aqueous adhesive, wherein the polarizing plate is dried using the drying method to provide.

According to the drying method of the present invention, it is possible to uniformly dry the optical film using the contact type drying method using the heating plate rotating body, to improve the drying efficiency, to reduce the variation in the moisture content in the width direction, .

1 is a process sectional view schematically showing a drying method of an optical film according to the prior art.
2 is a process sectional view schematically showing a method for drying an optical film according to an embodiment of the present invention.
3 is a perspective view schematically showing a heating plate rotating body according to an embodiment of the present invention.
4 is a process sectional view schematically showing a drying method of an optical film according to another embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

2 is a process sectional view schematically showing a method for drying an optical film according to an embodiment of the present invention. 2, a drying method of an optical film according to an embodiment of the present invention includes a drying furnace 300 provided with a plurality of guide rolls 320a and 320b for bending a conveying path of the optical film 10 The optical film 10 is conveyed and the heating plate rotating body 340 is disposed between the guide rolls so as to rotate in contact with the optical film 10 so that the optical film 10 is uniformly contact dried.

3, the heating plate rotating body 340 includes an annular heating plate 342 which rotates in contact with the optical film 10 and a rotating plate 342 which is fixed inside the annular heating plate 342, And the annular heating plate 342 is supported by the heating roll 344 and rotated.

The annular heating plate 342 may be made of stainless steel or steel having good thermal conductivity. As shown in FIG. 3, it is preferable that a plurality of heating plate pieces are connected to form a loop so that rotation can be smoothly performed.

The heating roll 344 may be heated by a heating means (not shown) such as an electric heating device. The heating plate 342 which is in contact with the heating roll 344 heated by the heating means is heated, The optical film 10, which is guided and moved while being in contact with the heating plate 342, receives heat required for drying from the optical film 10.

In one embodiment of the present invention, the heating plate rotating body moves in a state in which the optical film 10 is in contact with the upper surface of one heating plate rotating body 340, as shown in FIG. 2, And may be arranged to move in contact with the surface.

In another embodiment of the present invention, the heating plate rotating body is disposed in two stages in the drying furnace 300, as shown in FIG. 4, so that the optical film 10 is rotatably supported by the first heating plate rotating body 340a It may be configured to move in contact with the upper surface and then move in contact with the lower surface of the second heating plate rotating body 340b.

In the embodiment of the present invention, the optical film 10 is not particularly limited as long as it is a film requiring a drying step in a manufacturing process such as a polarizing plate.

In one embodiment of the present invention, the temperature of the drying furnace 300 may be appropriately selected in the range of 40 to 100 占 폚, preferably 60 to 100 占 폚.

An embodiment of the present invention is a method of manufacturing a polarizing plate in which a protective film is bonded to at least one surface of a polarizer using an aqueous adhesive, wherein the polarizing plate is dried by using the drying method described above .

The polarizer is prepared by dyeing and orienting a hydrophilic polymer film with iodine. As the hydrophilic polymer film, a polyvinyl alcohol film, a partially saponified polyvinyl alcohol film, or the like is used.

The polyvinyl alcohol film may have a degree of polymerization of usually 500 to 10,000, preferably 1,000 to 6,000, and more preferably 1,400 to 4,000. In the case of the saponified polyvinyl alcohol film, It is preferably 95.0 mol% or more, more preferably 99.0 mol% or more, and even more preferably 99.9 mol% or more.

The kind of the hydrophilic polymer film is not particularly limited as long as it is a film that can be stained with iodine in addition to a polyvinyl alcohol film. For example, a hydrophilic polymer film such as a polyethylene terephthalate film, an ethylene-vinyl acetate copolymer film, an ethylene-vinyl alcohol copolymer film, a cellulose film and a partially saponified film thereof, and a hydrophilic polymer film such as a dehydrated polyvinyl alcohol film And polyene-oriented films such as dehydrochlorinated polyvinyl chloride and the like can be used.

The thickness of the polarizer is not particularly limited, but is, for example, in the range of 5 to 40 占 퐉, preferably in the range of 10 to 30 占 퐉, and more preferably in the range of 15 to 25 占 퐉.

In the method for producing a polarizer, a polarizer produced through a swelling step, a dyeing step and a crosslinking step is washed with water and dried to prepare a polarizer.

The swelling step is carried out by immersing the unstretched polyvinyl alcohol film in a swelling tank filled with a swelling aqueous solution before dyeing to remove impurities such as dust and anti-blocking agent deposited on the surface of the polyvinyl alcohol film, Is a step for improving physical properties of the polarizer by swelling the alcoholic film to improve the stretching efficiency and preventing uneven dyeing.

Water (pure water, deionized water) can usually be used as a swelling aqueous solution, and when a small amount of glycerin or potassium iodide is added thereto, the swelling of the polyvinyl alcohol film can be improved and the processability can be improved. The content of glycerin is preferably 5% by weight or less based on 100% by weight of the aqueous swelling solution, and the content of potassium iodide is preferably 10% by weight or less.

The swelling bath temperature is preferably 20 to 45 캜, more preferably 25 to 40 캜. The execution time (swelling tank immersion time) of the swelling step is preferably 180 seconds or less, more preferably 90 seconds or less. When the immersion time is within the above range, it is possible to prevent the swelling from becoming excessive and saturation, to prevent breakage due to softening of the polyvinyl alcohol film and to improve the polarization degree by uniformly adsorbing iodine in the dyeing step have.

The stretching step may be carried out together with the swelling step, wherein the stretching ratio is preferably about 1.1 to 3.5 times.

The swelling step may be omitted and the swelling may be performed simultaneously in the staining step.

The dyeing step is a step of immersing a polyvinyl alcohol film in a dyeing tank filled with an aqueous solution for dyeing containing iodine to adsorb iodine on the polyvinyl alcohol film.

The dyeing aqueous solution may comprise water, a water-soluble organic solvent or a mixed solvent thereof and iodine. The content of iodine is preferably 0.4 to 400 mmol / L, more preferably 0.8 to 275 mmol / L, even more preferably 1 to 200 mmol / L.

To further improve the dyeing efficiency, iodide may be further included as a dissolution aid. As the iodide, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide may be used alone or in combination of two or more. Of these, potassium iodide is preferable in view of high solubility in water. The content of iodide is preferably 0.01 to 10% by weight, more preferably 0.1 to 5% by weight, based on 100% by weight of the dyeing aqueous solution.

The temperature of the dye bath is preferably 5 to 42 캜, more preferably 10 to 35 캜. The immersing time of the polyvinyl alcohol film in the dyeing tank is not particularly limited, and is preferably 1 to 20 minutes, and more preferably 2 to 10 minutes.

The dyeing step and the stretching step may be carried out. In this case, the cumulative stretching ratio is preferably 1.1 to 4.0 times. In the present specification, "cumulative stretching ratio" represents the value of the product of the stretching ratio at each step.

The crosslinking step is a step of immobilizing the adsorbed iodine molecules by immersing the dyed polyvinyl alcohol film in a crosslinking aqueous solution so that the dyeability due to physically adsorbed iodine molecules is not lowered by the external environment. The dichroic dyes are not often eluted in the humidity environment, but iodine molecules often dissolve or sublimate depending on the environment when the crosslinking reaction is unstable, and sufficient crosslinking reaction is required. In addition, the crosslinking step is important because, in order to orient the iodine molecules positioned between all the polyvinyl alcohol molecules and the molecules and to improve the optical properties, the crosslinking step generally needs to be elongated to the largest stretching ratio.

The aqueous solution for crosslinking may further comprise water as a solvent, and boron compounds such as boric acid, sodium borate, and iodide, and may further comprise an organic solvent mutually soluble with water.

The boron compound imparts short crosslinking and rigidity to suppress wrinkling during processing, thereby improving handling properties and forming iodine alignment.

The content of the boron compound is preferably 1 to 10% by weight, more preferably 2 to 6% by weight, based on 100% by weight of the aqueous crosslinking solution. When the content is less than 1% by weight, the crosslinking effect of the boron compound is reduced and it is difficult to impart rigidity. When the content is more than 10% by weight, the crosslinking reaction of the inorganic crosslinking agent is excessively activated and the crosslinking reaction of the organic crosslinking agent is difficult to proceed effectively.

Iodide is used to prevent the uniformity of the degree of polarization in the plane of polarizers and the desorption of dyed iodine. The iodide may be the same as that used in the dyeing step, and its content may be 0.05 to 15% by weight, preferably 0.5 to 11% by weight, based on 100% by weight of the aqueous crosslinking solution. If the content is less than 0.05% by weight, the iodide ion in the film may escape to increase the transmittance and the color value of the polarizer may be changed. Further, if the content exceeds 15% by weight, There is a problem that the transmittance is reduced due to penetration into the film.

The temperature of the crosslinking bath is 20 to 70 ° C, and the immersion time of the polyvinyl alcohol film in the crosslinking bath may be 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

The stretching step may be performed together with the crosslinking step, and in this case, it is preferable that the total stretching ratio is 3.0 to 8.0 times.

As described above, the stretching step may be performed in conjunction with the swelling step, the dyeing step and the crosslinking step, and may be carried out as an independent stretching step using a separate stretching tank filled with the eluting aqueous solution after the crosslinking step.

The washing step is a step of immersing the crosslinked and stretched polyvinyl alcohol film in a water bath filled with water for washing to remove unnecessary residues such as boric acid attached to the polyvinyl alcohol film in the previous steps.

The aqueous solution for washing may be water, and iodide may be further added thereto.

The temperature of the water bath is preferably 10 to 60 ° C, more preferably 10 to 40 ° C. The running time of the washing step is usually 1 to 60 seconds, preferably 3 to 30 seconds, and more preferably 5 to 20 seconds.

The wash step may be performed each time previous steps such as dyeing step, crosslinking step or stretching step are completed. It may also be repeated one or more times, and the number of repetition is not particularly limited.

The drying step is a step of drying the washed polyvinyl alcohol-based film and further improving the orientation of the iodine molecules dyed by the necking by drying, thereby obtaining a polarizer excellent in optical characteristics.

As the drying method, natural drying, air drying, heating and drying, far infrared ray drying, microwave drying, hot air drying and the like can be used. Recently, microwave drying in which only water in the film is activated and dried is newly used, Drying is mainly used. For example, it may be hot air dried at 20 to 90 DEG C for 1 to 10 minutes. The drying temperature is preferably low in order to prevent deterioration of the polarizer, more preferably 80 deg. C or lower, still more preferably 70 deg. C or lower.

As the protective film, a film excellent in transparency, mechanical strength, thermal stability, moisture barrier property and isotropy can be used. Specific examples thereof include polyesters such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate and polybutylene terephthalate Based resin; Cellulose-based resins such as diacetylcellulose and triacetylcellulose; Polycarbonate resin; Acrylic resins such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Styrene resins such as polystyrene and acrylonitrile-styrene copolymer; Polyolefin resins such as polyethylene, polypropylene, cycloolefins or polyolefins having a norbornene structure, and ethylene-propylene copolymers; Vinyl chloride resin; Amide resins such as nylon and aromatic polyamide; Imide resin; Polyether sulfone type resin; Sulfone based resin; Polyether sulfone type resin; Polyether ether ketone resin; A sulfided polyphenylene resin; Vinyl alcohol-based resin; Vinylidene chloride resins; Vinyl butyral resin; Allylate series resin; Polyoxymethylene type resin; A thermoplastic resin such as an epoxy resin, and the like. A film composed of the blend of the thermoplastic resin may also be used. Further, a film made of a thermosetting resin such as (meth) acrylic, urethane, acrylic urethane, epoxy, or silicone or a film made of an ultraviolet curable resin may also be used.

The content of the thermoplastic resin in the protective film may be 50 to 100% by weight, preferably 50 to 99% by weight, more preferably 60 to 98% by weight, even more preferably 70 to 97% by weight. When the content is less than 50% by weight, the inherent high transparency of the thermoplastic resin may not be sufficiently exhibited.

The protective film may contain one or more suitable additives. Specific examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a mold release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment and a colorant.

The protective film can be subjected to known surface treatments such as saponification treatment, corona treatment, plasma treatment, and easy adhesion layer treatment to facilitate adhesion with the polarizer.

Specific examples of the water-based adhesive include an isocyanate-based adhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive, a vinyl-based latex-based, an aqueous polyurethane and a water-based polyester. Among them, a polyvinyl alcohol-based adhesive is preferable. The water-based adhesive may suitably contain a crosslinking agent.

For example, a polyvinyl alcohol-based adhesive containing a crosslinking agent is usually used as an aqueous solution. The concentration of the aqueous solution is not particularly limited, but it is 0.1 to 15% by weight, preferably 0.5 to 10% by weight, more preferably 0.5 to 5% by weight in consideration of the coating property or the stability of standing.

Further, the adhesive may be further added with a coupling agent such as a silane coupling agent or a titanium coupling agent, various tackifiers, ultraviolet absorbers, antioxidants, heat stabilizers, stabilizers such as hydrolysis stabilizers and the like.

A water-based adhesive for bonding the polarizer and the protective film is applied to either side of the polarizer or the protective film or both. The coating operation is not particularly limited, and various methods such as a roll method, a spray method, and a dipping method can be used. It is preferable that the adhesive layer is applied so that the thickness of the adhesive layer formed after drying is 10 to 1,000 nm, preferably 40 to 600 nm, considering the solid content. If the thickness is less than 10 nm, the adhesive force may be poor. If the thickness is more than 1,000 nm, uniform application of the adhesive may be difficult or thickness unevenness may occur, resulting in poor appearance. Also, a tension may be applied to the protective film when the polarizer and the protective film are bonded, but it is preferable that the tensile force is as low as possible since the protective film deforms.

After the water-based adhesive is applied, the polarizer and the protective film are bonded together using a roll laminator or the like. After bonding the polarizer and the protective film, a drying process is performed to form an adhesive layer comprising a coating and drying layer.

As the drying method, the above-mentioned drying method of the optical film is used. Thus, the unevenness of the polarizing plate, the color misregistration in the width direction, and the variation in the moisture content in the width direction can be reduced.

The polarizing plate produced by the manufacturing method according to one embodiment of the present invention is characterized in that a surface treatment layer such as a hard coating layer, an antireflection layer, an antiglare layer, and an antistatic layer is further laminated on the other surface of a protective film not bonded to the polarizer, . Further, an optical functional film can be further laminated by a pressure-sensitive adhesive layer. Specific examples of the optical functional film include an optical compensation film in which a liquid crystalline compound or its polymer compound is oriented on the surface of a substrate, Polarized light of the opposite nature includes a reflective polarized light separation film to be reflected, a retardation film including a polycarbonate resin, and a retardation film including a cyclic polyolefin-based resin.

The polarizing plate produced by the manufacturing method according to one embodiment of the present invention can be used in a liquid crystal display device. The liquid crystal display device of the present invention can be manufactured by peeling off the peelable release film of the polarizing plate with a pressure-sensitive adhesive and then attaching the pressure-sensitive adhesive layer to the liquid crystal panel.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that the following examples are intended to illustrate the invention only and are not intended to limit the scope of the invention.

Production Example 1: Production of Polarizer

A transparent unstretched polyvinyl alcohol film (VF-PS, KURARAY Co.) having a degree of saponification of 99.9% or more was immersed in water (deionized water) at 30 ° C for 2 minutes and swelled. Then, 3.5 mM of iodine and 2 wt% of potassium iodide Was immersed in an aqueous solution for dyeing at 30 DEG C for 4 minutes to be dyed. At this time, stretching was performed at 1.3 times and 1.4 times at the swelling and dyeing stages, respectively. Subsequently, it contained 10% by weight of potassium iodide and 3.7% by weight of boric acid and was immersed in an aqueous crosslinking solution at 50 캜 for 2 minutes to crosslink. At this time, the crosslinking step was such that the total cumulative stretching ratio was 5.8 times. After the crosslinking was completed, the resultant was rinsed with water for 10 seconds at 20 DEG C for 20 seconds. The washed polyvinyl alcohol film was dried in an oven at 70 DEG C for 4 minutes to prepare a polarizer.

Production Example 2: Production of PVA-based adhesive

To 100 parts by weight of distilled water, 3 parts by weight of a carboxyl group-modified PVA resin (Kurarevo KL318, Kuraray Co., Ltd.) and 1.5 parts by weight of a polyamide epoxy resin (Sumirez resin 650 (solid content 30%), Sumitomo Chemical Co., To prepare an adhesive.

Examples 1 to 6 and Comparative Examples 1 to 6: Preparation of Polarizing Plate

A triacetyl cellulose protective film having a thickness of 80 占 퐉 was placed on both sides of the PVA polarizer obtained in Production Example 1 and then bonded to each other using the PVA adhesive prepared in Production Example 2, To prepare a polarizing plate.

Experimental Example 1:

The properties of the thus-prepared polarizing plate were measured as described below, and the results are shown in Table 1 below.

(1) Stain Lv

The form of occurrence of the spots (wrinkles) generated in the stretching direction was defined by the size in the width direction (mm) and visually evaluated.

<Evaluation Criteria>

1 Level: Width 0.5 or less

2 Level: width less than or equal to 0.8

3 Level: Width 1.2 or less

4 Level: width less than 1.5

5 Level: Width greater than 1.5

(2) Width direction group color b

The color band b was measured using a spectrophotometer (V-7100, manufactured by Jasco) at an extinction ratio.

(3) Wet water content (%)

IRMA1100S from CHINO Co., Ltd., using an infrared reflection three-wavelength system, was used to measure the moisture content in the wetter.

division dry
Way Temperature dry
time
(sec) stain
Lv Width direction group color b Wet Moisture Content (%) Deviation
(△) left
End center Right end Deviation
(△) Left end center Right end Example 1 2, 85 120 One 0.2
Below 1.3 1.1 1.2 0.2
Below 2.4 2.6 2.5 Example 2 2, 75 120 One 0.3
Below 1.3 1.0 1.1 0.2
Below 2.4 2.6 2.5 Example 3 2, 65 120 One 0.3
Below 1.2 0.9 1.0 0.2
Below 2.5 2.7 2.6 Example 4 2, 85 180 One 0.1
Below 1.3 1.2 1.2 0.2
Below 2.3 2.5 2.3 Example 5 2, 75 180 One 0.3
Below 1.3 1.0 1.2 0.2
Below 2.3 2.5 2.3 Example 6 2, 65 180 One 0.3
Below 1.2 0.9 One 0.2
Below 2.4 2.6 2.4 Comparative Example 1 1, 85 120 4 0.6 1.2 0.6 0.8 0.4 2.5 2.9 2.6 Comparative Example 2 1, 75 120 4 0.7 1.3 0.6 0.9 0.4 2.6 3.0 2.7 Comparative Example 3 1, 65 120 4 0.8 1.3 0.5 0.8 0.5 2.6 3.1 2.6 Comparative Example 4 1, 85 180 3 0.6 1.3 0.7 0.8 0.4 2.4 2.8 2.5 Comparative Example 5 1, 75 180 4 0.7 1.3 0.6 0.9 0.4 2.4 2.8 2.4 Comparative Example 6 1, 65 180 4 0.7 1.3 0.6 0.8 0.4 2.5 2.9 2.6

As shown in Table 1, the polarizing plates of Examples 1 to 6 prepared according to the drying method of the present invention had a larger width and a larger width than the polarizing plates of Comparative Examples 1 to 6, It was confirmed that the deviation in the directional group color b and the wilting moisture percentage was small.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Do. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the actual scope of the invention is defined by the appended claims and their equivalents.

10: Optical film; 30, 300: drying furnace
32a, 32b, 320a, 320b: guide rolls; 34: Hot Air Injection Pipe
34a: hot air outlet; 340: Heating plate rotating body
342: heating plate; 344: heat roll

Claims (9)

The optical film 10 is conveyed through the drying furnace 300 provided with the plurality of guide rolls 320a and 320b for bending the conveying path of the optical film 10 and the heating plate rotating body 340 Is disposed so as to rotate in contact with the optical film (10) so that the optical film (10) is contact-dried. The heating plate rotating body (340) according to claim 1, wherein the heating plate rotating body (340) comprises an annular heating plate (342) rotating in contact with the optical film (10) 344) are provided, and the annular heating plate (342) is supported by the heating roll (344) while rotating. The method of claim 2, wherein the annular heating plate (342) is made of stainless steel or steel. The method of claim 2, wherein the annular heating plate (342) connects the plurality of heating plate pieces to form a loop. The heating plate rotating body according to claim 1, wherein the heating plate rotator is configured to move the optical film (10) in contact with the upper surface of one heating plate rotating body (340) and then move to contact the lower surface A method of drying a film. The method according to claim 1, wherein the heating plate rotating body is disposed in two stages in the drying furnace (300) to move the optical film (10) in contact with the upper surface of the first heating plate rotating body (340a) And is moved to contact the lower surface of the second heating plate rotating body (340b). The method for drying an optical film according to claim 1, wherein the optical film is a polarizing plate. The method for drying an optical film according to claim 1, wherein the temperature of the drying furnace is 40 to 100 占 폚. A process for producing a polarizing plate in which a protective film is bonded to at least one surface of a polarizer with an aqueous adhesive, comprising the step of drying the polarizing plate thus bonded using the drying method according to any one of claims 1 to 8 A method for producing a polarizing plate.

Images